Lopez's third studio album This Is Me... Then was released in November 2002. It featured Lopez on a more "hands-on role" than ever before, writing more material.[1] Her fiancé at the time, actor Ben Affleck, was her muse and inspiration for the album's lyrics; the title referred to "who you are are at the time", and it was a record that wanted to look back on in the future.[2] Affleck and Lopez became a prominent supercouple in popular culture, referred to as "Bennifer" by the public.[3] "Jenny from the Block" was released as the album's lead single, peaking at number three on the US Billboard Hot 100, while its second single "All I Have", topped the Hot 100. However, Lopez was initially dissatisfied with the release of both singles. She felt that the tracks were too similar to her previous singles such as "Ain't It Funny" and "I'm Real"; she felt like she was "visiting old territory". "Those tracks were like a different era for me, and I didn't want people to perceive it like I'm just trying to capitalize on the same thing. But the record company was like, 'Who cares what they think, those are hits mama!'". Lopez, who stated she "calls the shots", eventually agreed.[4] She subsequently released "I'm Glad" as the album's third single, with it being serviced to Top 40 radio on April 8, 2003.[5]

"I'm Glad" is an uptempo R&B ballad which runs for a duration of three minutes and forty-two seconds.[6][7] Lopez wrote the song with the assistance of Troy Oliver, Cory Rooney, Andre Deyo and Schooly D, with Oliver and Rooney serving as producers. The singer recorded her vocals for the track with Peter Wade Keusch and Bruce Swedien at The Hit Factory recording studios in New York City, where it was also mixed. "I'm Glad" contains a sample of the 1986 Schooly D song "P.S.K. What Does It Mean?".[8] It's instrumentation consists of classical harp runs laced throughout a computer-generated beat.[9] Written in the key of Db Major, Lopez's vocal spans from an A3 to a C5; piano and guitar are also utilized in "I'm Glad".[10] Lyrically, "I'm Glad" is about finding true love, containing lyrics such as "I think I'm in love. Damn, finally".[11]The Boston Globe noted the song's lyrics to be about her relationship with actor Ben Affleck, who served as Lopez's muse for This Is Me... Then.[9]

The music video for "I'm Glad" was filmed in February 2003.[12] While coming up with ideas for the video, Lopez's sole vision was to create a scenario where she could dance solo, without back-up dancers or any other assistance. She then hired David LaChapelle to direct the music video, and he came up with the idea to recreate the film Flashdance (1983). Eventually, LaChapelle identically fashioned the "sets, iconography, and costuming" of Flashdance as a back-drop for Lopez to dance.[13] For the music video, Lopez sported her natural curly hair,[14] leotards and "tiny pants".[15] She spent several hours at night perfecting the music video, taking part in the editing process herself.[4] During the music video's editing stages, Lopez wanted to make sure everything was authenticate. She stated:

"I really worked out and did the diet thing... and then after the video...there's always that one guy who's like "We should retouch this". I was like, "You're going to leave everything the way it is. That's how it wiggles and jiggles in real life, that's how they're going to see it in the video. And I noticed—[the editors] sent [the video] to me and they have shaved off a little bit of my hips and—I was like, "That ain't me—those are not my hips. Just leave them the way they are. Do me a favor—don't touch my hips. Don't try to make me look skinnier. It's fine, it's fine the way it is". And that's what they did."[16] Prior to the video's release, Jon Wiederhorn of MTV News reported that the clip was heavily influenced by the '80s, stating "Lopez strikes '80s dance moves, and the color, style and camerawork have a decidedly retro vibe".[12]

The clip begins with Lopez entering a dance studio wearing a puffy jacket and scarf. She has arrived at an audition, with a table of judges present. Suddenly, the screen switches to showing different aspects of her life, including her at her modest home, riding through the neighborhood on a bike with her dog running along, as well as her role as an exotic dancer at a local bar and grill. Later, at a strip club, she is seen dancing to intricate choreography clothed in a skimpy red top. She then appears exercising and practicing her dance moves in another location. The screen then switches to before she entered the dance audition; she walks through a line of intimidating beautiful ballerinas. Lopez's dance routine in front of the judges then commences her audition, which includes her dancing on the judge's table, as they move their feet to the music.[16]

The clip for "I'm Glad" earned Lopez acclaim for her physique and choreography. K. Thor Jensen of UGO Networks placed the music video seventeenth on a list of the "50 Sexiest Music Videos of All Time", calling it a "funky" homage to Flashdance that has "J-Lo in several scenes from the classic flick, dancing like her life depended on it". Jensen wrote, "The video would earn a spot on this list just for the bit where water pours down from the ceiling on Lopez, but luckily the rest of the clip keeps the quality high".[17] Similarly, Joe Usmar of Daily Mirror placed the music video on a list of "10 Sexiest Music Videos Ever Made". Usmar described it as "goddamn hawt".[15]

Author and professor Daniel Bernardi observed in The Persistence of Whiteness: Race and Contemporary Hollywood Cinema (2013): "While Beal's performance was criticized for its lack of dance, Lopez's bodily performance faced scrutiny for its excess".[18] In the book Dance and the Hollywood Latina: Race, Sex, and Stardom (2011), author Priscilla Peña Ovalle noted that the music video's provocative sexual choreography "authenticated [Lopez] as a bona fide Hollywood Latina by showing her dancing in shots that tilt from face to fanny".[19] Ovalle also stated that the storyline of Flashdance was similar to Lopez's life, and she fully embodied a "fantasy of achievement".[13] Similarly, Gary Susman of Time wrote: "In a way, of course, Lopez was re-enacting her own life story, that of the Bronx girl who’d used street moves to dance her way to fame. Unlike Flashdance, “I’m Glad” starred a woman who could perform her own dance moves."[20] The video was nominated for four MTV Video Music Awards.[15]

The recreation of dance sequences from Flashdance led the film's production company, Paramount Pictures, to sue Lopez and Sony Music over copyright infringement claims.[21] A spokesperson for Lopez said that the film is one of Lopez's "favorite" movies, and that clip was nothing but a tribute to it.[22] Paramount and Sony settled out of court.[20] Apart from this, Mauren Marder—whose life was the inspiration for Flashdance—sued Lopez and Sony for copyright infringement in November 2003.[23] Additionally, Marder had previously also sued Paramount for only paying her a $2,300 fee for her story, which the film adaption of grossed over $150 million at the United States box office.[24] Marder "had refused to grant sequel rights or to permit any further use of her story or identity after the film became a success" according to her attorney, Robert Hefling. Hefling stated, "She is penniless, disabled with a spinal injury, and trying to raise a teenage daughter. Now her life story is on the screen again—and other people are profiting from it—with no acknowledgment of her rights, let alone fair compensation for her contribution."[25] In June 2006, all of Marder's claims were dismissed.[24]